The Tower Bridge website: a new benchmark in sustainability

For a globally recognised heritage site, sustainability doesn’t stop at the physical world. A 2021 study suggested that digital sector emissions contribute to 2.1%–3.9% of global emissions, and even at the bottom of that estimate, it's obvious that digital emissions, though often unseen, have a measurable real world impact. 

At Ten4 Design we are committed to developing sustainable digital products, so when we began working on the new Tower Bridge website we were excited to see that sustainability was given high-billing in the brief.

Our work re‑engineering the Tower Bridge website shows that performance and sustainability go hand in hand.

Our first step was to comprehensively audit the CO₂e (carbon dioxide equivalent) for the 25 most visited pages on the Tower Bridge website, using the Sustainable Web Design Model (SWDM).

Our research found:

• The average page on the Tower Bridge website produced 0.60g CO₂e per page-view
• The site as a whole produced around 2.8 metric tonnes of CO₂e per year — roughly equivalent to driving from London to Cape Town or powering a UK home for more than a year.
• The most visited page by far (940k page-views per year) was also the least efficient by far (1.57g CO₂e per page-view)

Benchmarking against equivalent organisations

Benchmarked against other top London visitor attractions’ websites, Tower Bridge fared better than average, but was firmly in the middle of the field.

• The London Eye: 1.24g CO₂e — the highest of the group
• Tower of London: 0.92g CO₂e
• St Paul’s Cathedral: 0.63g CO₂e
• Tower Bridge: 0.60g CO₂e per page view
• Westminster Abbey: 0.55g CO₂e
• Kew Gardens: 0.47g CO₂e — the lowest of the group

Average (across all sites): 0.73g CO₂e

Following a full redesign and optimisation programme, we exceeded our own ambitions. Our base target was a 50% reduction in CO₂e, with a stretch target of 70%, but at launch, the top five most visited pages produce 75% less CO₂e than before, rising to an 81.2% reduction when looking at the whole website.

On the website’s homepage alone, compressing a background video saved a whopping quarter of a tonne in CO₂e annually.

The site’s emissions per page reduced from 0.52g to just 0.09g CO₂e per page view, making Tower Bridge the most efficient of all the sites we benchmarked and saving an-estimated 2.38 tonnes of CO₂e each year. In short, it now generates only a fifth of its previous emissions while offering visitors a faster, smoother experience.

Our approach centred on reducing unnecessary computation and data transfer without compromising usability, accessibility, or design quality.

We achieved this by:

• Making carbon-conscious design decisions — adopting a whole-project approach, rather than treating sustainability as a late-stage developer-fix
• Reducing database queries — streamlining how data is fetched and served.
• Implementing aggressive caching — ensuring that content loads from memory instead of regenerating on every visit.
• Optimising assets — converting images to next‑gen formats, compressing media, and minimising scripts.
• Eliminating redundant requests — particularly from third‑party integrations and APIs.

Every kilobyte saved translates directly into lower energy use and fewer emissions. Cumulatively, these improvements in technical efficiency deliver a meaningful climate impact. 

Following our work, every visit to the Tower Bridge website is now faster, lighter, and greener, proving that even small design and development choices can have a big environmental impact.

Continuous measurement for long term CO₂e management 

To ensure we continue to manage Tower Bridge’s digital carbon footprint, we are monitoring the site using Digital Carbon Online — a platform that automatically tracks, reports and helps reduce the carbon footprint of entire websites over time.

It provides clear, credible carbon assessments following the SWDM, giving Tower Bridge continuous visibility of website emissions, performance trends and opportunities for carbon reduction.

From a decidedly mid-field starting point, Tower Bridge has moved into a clear leadership position. With emissions around 81% lower than its nearest peer (Kew Gardens), it sets a new benchmark for low‑carbon web design in the visitor attraction sector.